copyrights

#!/usr/bin/env python

import io
import re
import sys
from collections import namedtuple
from operator import attrgetter
from itertools import groupby
from datetime import datetime
from subprocess import Popen, PIPE, DEVNULL
from pathlib import Path
from fnmatch import fnmatch
from functools import lru_cache


Contribution = namedtuple('Contribution', ('author', 'email', 'year', 'filename'))
Copyright = namedtuple('Copyright', ('author', 'email', 'years'))


def main():
    includes = {
        '**/*.py',
        '**/*.rst',
    }
    excludes = {
        'docs/examples/*.py',
        'docs/license.rst',
    }
    prefixes = {
        '.py': '#',
        '.rst': '..',
    }
    if len(sys.argv) > 1:
        includes = set(sys.argv[1:])
    contributions = get_contributions(includes, excludes)
    for filename, copyrights in contributions.items():
        filename = Path(filename)
        update_copyright(filename, copyrights, prefixes[filename.suffix])


def get_contributions(include, exclude):
    sorted_blame = sorted(
        get_blame(include, exclude),
        key=lambda c: (c.filename, c.author, c.email)
    )
    blame_by_file = {
        filename: list(file_contributions)
        for filename, file_contributions in groupby(
            sorted_blame, key=attrgetter('filename')
        )
    }
    contributors_all_years = {
        filename: {
            Copyright(author, email, frozenset(y.year for y in years))
            for (author, email), years in groupby(
                file_contributors, key=lambda c: (c.author, c.email)
            )
        }
        for filename, file_contributors in blame_by_file.items()
    }
    contributions = {
        filename: {
            Copyright(
                c.author, c.email,
                (min(c.years), max(c.years))
                if len(c.years) > 1 else
                min(c.years)
            )
            for c in contributors
        }
        for filename, contributors in contributors_all_years.items()
    }
    return contributions


def get_blame(include, exclude):
    for filename in get_source_files(include, exclude):
        blame = Popen(
            ['git', 'blame', '--line-porcelain', 'HEAD', '--', filename],
            stdout=PIPE,
            stderr=PIPE,
            universal_newlines=True
        )
        author = email = year = None
        for line in blame.stdout:
            if line.startswith('author '):
                author = line.split(' ', 1)[1].rstrip()
            elif line.startswith('author-mail '):
                email = line.split(' ', 1)[1].rstrip().lstrip('<').rstrip('>')
            elif line.startswith('author-time '):
                # Forget the timezone; we only want the year anyway
                year = datetime.fromtimestamp(int(line.split(' ', 1)[1].rstrip())).year
            elif line.startswith('filename '):
                yield Contribution(
                    author=author, email=email, year=year, filename=filename)
                author = email = year = None
        blame.wait()
        assert blame.returncode == 0


def get_source_files(include, exclude):
    ls_tree = Popen(
        ['git', 'ls-tree', '-r', '--name-only', 'HEAD'],
        stdout=PIPE,
        stderr=DEVNULL,
        universal_newlines=True
    )
    if not include:
        include = {'*'}
    for filename in ls_tree.stdout:
        filename = filename.strip()
        if any(fnmatch(filename, pattern) for pattern in exclude):
            continue
        if any(fnmatch(filename, pattern) for pattern in include):
            yield filename
    ls_tree.wait()
    assert ls_tree.returncode == 0


insertion_point = object()
def parse_source_file(filename, prefix):
    license = get_license()
    license_start = license[0]
    license_end = license[-1]
    with filename.open('r') as source:
        state = 'preamble'
        for linenum, line in enumerate(source, start=1):
            if state == 'preamble':
                if linenum == 1 and line.startswith('#!'):
                    yield line
                elif linenum < 10 and 'set fileencoding' in line:
                    yield line
                elif line.rstrip() == prefix:
                    pass # skip blank comment lines
                elif line.startswith(prefix + ' GPIO Zero:'):
                    pass # skip existing header lines
                elif line.startswith(prefix + ' Copyright (c)'):
                    pass # skip existing copyright lines
                elif line.startswith(prefix + ' ' + license_start):
                    state = 'license' # skip existing license lines
                else:
                    yield insertion_point
                    state = 'blank'
            elif state == 'license':
                if line.startswith(prefix + ' ' + license_end):
                    yield insertion_point
                    state = 'blank'
                    continue
            if state == 'blank':
                # Ensure there's a blank line between license and start of the
                # source body
                if line.strip():
                    yield '\n'
                yield line
                state = 'body'
            elif state == 'body':
                yield line


def update_copyright(filename, copyrights, prefix):
    print('Re-writing {filename}...'.format(filename=filename))
    license = get_license()
    copyrights = sorted(
        copyrights, reverse=True, key=lambda c:
            (c.years[::-1] if isinstance(c.years, tuple) else (c.years, 0), c.author)
    )
    content = []
    for line in parse_source_file(filename, prefix):
        if line is insertion_point:
            if len(content) > 0:
                content.append(prefix + '\n')
            content.append(
                prefix + " GPIO Zero: a library for controlling the "
                "Raspberry Pi's GPIO pins\n")
            for copyright in copyrights:
                try:
                    start, end = copyright.years
                except TypeError:
                    years = str(copyright.years)
                else:
                    years = '{start}-{end}'.format(start=start, end=end)
                content.append(
                    prefix + " Copyright (c) {years} "
                    "{copyright.author} <{copyright.email}>\n"
                    "".format(years=years, copyright=copyright))
            content.append(prefix + '\n')
            content.extend(
                (prefix + ' ' + l).strip() + '\n'
                for l in license
            )
        else:
            content.append(line)
    # Yes, if I was doing this "properly" I'd write to a temporary file and
    # rename it over the target. However, I'm assuming you're running this
    # under a git clone ... after all, you are ... aren't you?
    with filename.open('w') as target:
        for line in content:
            target.write(line)


@lru_cache()
def get_license():
    with io.open('LICENSE.rst', 'r') as text:
        return text.read().splitlines()


if __name__ == '__main__':
    main()